Hessitation in Late Model Subarus

[Bruce Plecan]

>>The ECU is a OBD2 type with EPROM.
> > What I would like to do is simply reduce the sensitivity of the sensor.

That's not the problem as I see it.  It's seeing a knock you don't want it
to see.
That is a problem with all these dumb acoustic sensors, only cure is going
to ionization kknock detection, please refer to the archives and search ION.

> > That is what I did mechanically and it seemed to work pretty good.  The
> > problem though is that it is a little iffy and esoteric and problematic
> > and lacking consistency.  It is not solid state enough to suit me.  I'd
> > rather dampen the signal electrically.

OK, once you get it dampened how ya know it really works when you need it?.
Ya just listen for it?.   I'd be a heck of alot more curious about the cause
for it, what gas are you using. operating temp., spark plug heat
range/style.  If you've already addressed these fine, but you didn't mention
them.  I just don't beleive in automatically disabling parts of the ecm.
How about the self diagnostics of OBDII, what are it's parameters, and what
effect would it have on it.

> > I tried hooking up a variable capacitor in parallel with it.  I thought
> > that this would let any voltage spikes bleed (partially) to ground and
> > lessen the signal strength arriving at the ECU.  I had trouble with this
> > method because as soon as I turned the capacitor a certain amount, I'd
> > get a trouble code and would have to shut down and restart.  I'll guess
> > that the ECU sends a monitor current through the sensor and detects when
> > it is not at the proper impedance.  It didn't seem to help either.  I am
> > not convinced that I was doing the wrong thing either.  I just could not
> > get any positive results.

> > I thank you for your attention Fellows and thank you in advance for any
> > suggestions.
> > GARY       mailto:hobiegary at earthlink.net
> > Have you thought about a high resistance pot set up as a voltage divider
> on the sensor? Cut the output down to about 80% and see if it still false
> triggers. Then take it back up to the point where the performance "just"
> starts to deteriorate. I have not tried this, but as the sensor is just a
> microphone, I figure a volume control should do the trick.